The present invention relates to a bumper beam structure that constitutes a bumper of a vehicle such as an automobile.
A vehicle is provided at a front end thereof with a bumper beam that extends in the vehicle-width direction to protect an occupant and the body of the vehicle against an impact load coming from ahead of the vehicle.
In the event of, for instance, a high-speed collision of the vehicle or a major collision, the bumper beam preferably collapses to as large an extent as possible by minimizing the extent to which its portions remain intact, thereby absorbing as much impact energy as possible. On the other hand, in the event of, for instance, a low-speed collision of the vehicle or a minor collision, the bumper beam preferably minimizes the extent of intrusion of an object with which the vehicle has collided to keep the vehicle body as undamaged as possible, thereby minimizing the cost, including part replacement costs, for repairing damage that the vehicle body sustains from the collision.
A bumper beam structure that accommodates both a high-speed collision and a low-speed collision has long had a bumper beam having an increased closed section area or having an increased plate thickness, thereby improving the bearing capacity of the bumper beam.
In addition, there is known a bumper beam structure having a reinforcing member provided inside the closed section of the bumper beam. In a bumper beam structure described in, for instance, Japanese Unexamined Patent Application Publication (JP-A) No. 2008-260364, a reinforcing member having a hat-shaped horizontal section is mounted inside the closed section of the bumper beam at the center in the vehicle-width direction of the bumper beam. In such a reinforcing member, a hat-shaped opening faces the outside of the vehicle in the longitudinal direction of the vehicle. A flange on the opening is joined to an outer vertical wall that constitutes the closed section of the bumper beam, while a hat-shaped top member is joined to an inner vertical wall that constitutes the closed section of the bumper beam, whereby the flange and the top member are secured to the bumper beam. In addition, the reinforcing member has a pair of angled members that converge in the spacing in the vehicle-width direction therebetween from the hat-shaped opening toward the top member (namely, from the outside of the vehicle toward the inside).
However, an increased closed section area of the bumper beam or an increased plate thickness raises a problem such as an increase in vehicle body weight.
On the other hand, the bumper beam structure described in JP-A No. 2008-260364 has the reinforcing member disposed locally on the bumper beam (at the center in the vehicle-width direction), thereby achieving weight reduction compared with a conventional structure. In addition, damage to the vehicle body can be eliminated or reduced through the use of the reinforcing member in the event of a minor collision, while impact energy can be absorbed through the fracture of the reinforcing member in the event of a major collision.